Anthropologists have engaged little with the topic of collective action and with the relevant social scientific literature. This working paper seeks to respond to recent calls made within the discipline to engage with both. Drawing on fieldwork carried out among Latin Americans in London, this essay shows how their mobilization is shaped by a multiplicity of factors and not merely by the political opportunity structure of the country of arrival, as the prevailing approach to migrants' mobilizations seems to contend. In addition to indicating some of the other factors that influence migrants' mobilization, the paper makes some suggestions for rethinking the notion of political opportunity structure in more inclusive, loose, flexible and pluralist terms. Last but not least, this paper offers an account of how Latin American migrants are responding collectively to the difficulties they experience in Britain.